There are areas of application for bevel gears which require special standards in the matter of geometry, accuracy, etc. While the formation of the head edge of bevel gears only plays a subordinate role in numerous applications, thus, for example, the bevel gear specifications for helicopters require an accurately defined transition between the tooth flanks and the tooth heads.
Thus, for example, these bevel gear specifications require a radius of the head edges in the range between 0.005″ (0.127 mm) and 0.015″ (0.381 mm). The production of bevel gears in the range mentioned as an example is complex and susceptible to errors.